1. Field of the Invention
The present invention relates to a method of determining a reflective surface of a reflector of a vehicle lamp used in a vehicle such as an automobile, and a vehicle lamp.
2. Related Background Art
Regarding a vehicle lamp, in addition to (1) conditions relating to functionality as a lamp, because the vehicle lamp is used installed in a vehicle such as an automobile, there are also (2) conditions relating to shape (shape constraints) and (3) conditions relating to external appearance (appearance constraints). There are thus demands to realize a lamp fixture for which the conditions relating to functionality are optimized after given shape constraints and appearance constraints have been satisfied.
Regarding conditions from a functionality perspective, it is required that the lamp fixture gives a suitable light distribution pattern in accordance with the type of lamp fixture, for example light uniformity in which the whole of the lamp fixture emits light uniformly, or light diffusivity in which light is suitably diffused and can be seen from various directions may be required.
Moreover, with regard to constraints from a vehicle or vehicle body perspective, examples of shape constraints are conditions due to the volume and shape of the lamp fixture housing of the vehicle body and conditions due to the shape of the outer surface of the lamp fixture (the outer surface of the lens) having to be continuous with other parts of the vehicle body. Moreover, examples of appearance constraints are conditions due to requirements from a vehicle body design perspective and requirements that the external appearance of the lamp fixture be in harmony with the external appearance of other parts of the vehicle body.
In recent years, as designability of vehicles has improved, vehicle lamps that conform to yet more constraints from a vehicle body perspective, in accordance with the individual form of the vehicle, the type of lamp fixture (illuminating lamp, indicator lamp etc.) and so on, have come to be required. One such constraint from a vehicle body perspective is that the area and shape of indicator lamps such as front turn signal lamps on the vehicle body may be constrained from the perspective of the overall constitution of the vehicle body and a design perspective.
However, indicator lamps such as front turn signal lamps have a function of indicating the presence of the vehicle and the drivers"" intentions to people outside the vehicle. As a functional condition of an indicator lamp, it is thus required that the indicator lamp has a light distribution pattern such that light is emitted spread out over a prescribed range, so that the indicator lamp can be seen by people in various positions relative to the vehicle. If constraints from a vehicle body perspective as described above such as the indicator lamp having to occupy only a small area become strict, then it will be difficult to design an indicator lamp satisfying the required light distribution pattern conditions.
Specifically, a vehicle lamp is composed of a light source (light source bulb) disposed in a prescribed light source position, a reflector that reflects light from the light source bulb in the direction of an optical axis, and a lens that transmits the reflected light from the reflector and emits this reflected light to the outside. In a vehicle lamp having such a constitution, the light distribution pattern of the light emitted from the lamp fixture is controlled primarily by the surface shape of the reflective surface of the reflector that reflects the light from the light source bulb, and the shape of the lens through which the light passes.
However, if the area occupied by an indicator lamp on the vehicle body is restricted, then the total area of the reflective surface of the reflector will be restricted, and hence the solid angle of the reflective surface when viewed from the light source will become smaller. In the case of such an indicator lamp, to realize the conditions required of the light distribution pattern (the light distribution condition), it is necessary to utilize the light incident from the light source on the reflective surface at the restricted solid angle effectively as reflected light, and thus control the light distribution pattern obtained.
To solve the above problems, it is an object of the present invention to provide a method of determining the reflective surface of a reflector in a vehicle lamp, and a vehicle lamp, for which light from a light source is utilized effectively as reflected light and a reflective surface that satisfies a required light distribution condition can be determined efficiently.
To attain this object, the method of determining a reflective surface of a reflector used in a vehicle lamp according to the present invention comprises: (1) a basic condition setting step of setting basic conditions including a light source position in which a light source is disposed, an optical axis that is the direction in which light from the light source is reflected by a reflective surface of a reflector, and a reflective surface outline of the reflective surface as viewed from the direction of the optical axis; (2) a segmentation condition setting step of setting segmentation conditions including a segmentation axis that is perpendicular to the optical axis and designates the direction in which the inside of the reflective surface outline is segmented into a plurality of reflection regions, and a number of segments into which the inside of the reflective surface outline is segmented along the segmentation axis; (3) a reflection condition setting step of setting reflection conditions for each of the plurality of reflection regions, including a reflection angle that designates the direction in which light from the light source is reflected by a segment surface that forms the reflective surface in that reflection region in terms of the angle in the direction of the segmentation axis as viewed from the optical axis, and a solid angle condition that the solid angle of the segment surface when viewed from the light source should satisfy; and (4) a reflective surface determining step of, based on the basic conditions, the segmentation conditions and the reflection conditions, segmenting the inside of the reflective surface outline to generate the plurality of reflection regions, creating a surface shape of the segment surface corresponding to each of the plurality of reflection regions, and determining a surface shape that satisfies a prescribed light distribution condition for the whole of the reflective surface composed of the segment surfaces.
In the above-mentioned method of determining the reflective surface of a reflector in a vehicle lamp, firstly the reflective surface outline, on which there are restrictions due to requirements from a vehicle body constitution perspective and a design perspective, is set as a basic condition for reflective surface determination, with it specifically being the area and shape of the reflective surface as viewed from the direction of the optical axis that are set, and furthermore segmentation conditions and reflection conditions are set in accordance with the basic conditions such as this reflective surface outline. Then, based on these various conditions, the inside of the reflective surface outline is segmented along a segmentation axis to produce a plurality of reflection regions, a segment surface is created for each reflection region, and a surface shape for the reflective surface as a whole satisfying a required light distribution condition is determined.
According to such a reflective surface determination method, the reflection conditions on reflection of light from the light source by the reflective surface, and the light distribution pattern obtained from the reflected light, can be controlled separately for each of the segmented reflection regions and segment surfaces. Moreover, correlations in the reflection conditions and light distribution patterns between the segment surfaces can be controlled by setting correlations in advance in the reflection conditions such as the reflection angles set for the reflection regions. As a result, a reflective surface determination method is realized for which it is possible to utilize light from the light source more effectively in the reflection at the reflective surface, and a reflective surface that satisfies the required light distribution condition can be obtained efficiently.
Moreover, the vehicle lamp according to the present invention comprises a light source, a reflector having a reflective surface that reflects light from the light source in the direction of a prescribed optical axis, and a lens through which light reflected by the reflective surface passes, wherein the reflective surface of the reflector is such that the inside of a reflective surface outline is segmented into a plurality of reflection regions along a segmentation axis that is perpendicular to the optical axis by a plurality of segmentation lines that are approximately perpendicular to the optical axis and the segmentation axis, and, for each of the plurality of reflection regions, a surface shape of a segment surface which forms the reflective surface in that reflection region is formed in a surface shape having as a reflection axis the direction of a reflection angle in the direction of the segmentation axis as viewed from the optical axis, with the reflection angle being set for each of the reflection regions.
According to the vehicle lamp having such a constitution, the light distribution pattern due to each segment surface and the correlations between these light distribution patterns can be controlled easily and suitably. It is thus possible to reliably obtain a reflector for which the light distribution pattern due to the whole of the reflective surface made up of the plurality of segment surfaces satisfies a required light distribution condition, and a vehicle lamp having this reflector.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.